In-beam studies of M-centre production processes in NaCl

Measurements of F- and M-centre colour curves in NaCl during irradiation at temperatures between 15 and 95 degrees C and at dose rates of the order of 10 4 rad h -1 indicate quite clearly two distinct processes for M-centre production. One, the statistical process, leads to an M varies as F 2 relation at both low and high doses. The other, an F-centre thermal diffusion process, produces a deviation in this relationship and furthermore is responsible for the maximum observed in F-centre colour curves at high temperatures. These two processes, together with an interstitial trapping model, provide a comprehensive picture for the first-stage colouring process in NaCl, over the range of temperatures and dose rates used here.